The conducting of electrochemical reactions on a surface of a semiconductor substrate is known.
Conventionally, the semiconductor substrate and a counter-electrode are immersed in an electrolyte containing a species able to react on the surface of said substrate.
The surface of the substrate is then polarized using an electric power source at a potential permitting the envisaged reaction.
Depending on whether the envisaged reaction is anodic or cathodic, and depending on the type of conductivity—N or P—of the semiconductor substrate, it may be necessary to activate the reaction by illuminating the semiconductor substrate.
The aim of illumination is to excite the charge carriers of the semiconductor valence band to populate the conduction band, which corresponds to what is called activation of the surface of the semiconductor substrate.
If illumination provides energy that is greater than the difference between the valence and conduction bands—i.e. the gap—of the semiconductor, the charge carriers are able to take part in electrochemical reactions.
The conducting of such anodic or cathodic reactions has been subject of numerous patent applications and scientific publications.
Amongst the most known reactions, mention may be made of reactions concerning the porosification of silicon on n- or p-doped substrates, these reactions being mostly conducted in a hydrofluoric acid medium such as described in J. N. Chazalviel, “Porous Silicon Science and Technology”, Vial and Derrien Eds. Springer, Berlin 1995, 17-32.
One well-known electrochemical reaction on the surface of a semiconductor substrate is the grafting of organic molecules and polymers. Amongst these the following can be cited:                the grafting of methoxy groups from methanol;        electrochemical grafting reactions of alkyl groups via radicals formed anodically from organomagnesium compounds of RMgX type, or via radicals formed cathodically from alkane halides of RX type;        the grafting of phenyl groups from diazonium salts;        the grafting of vinyl polymers from diazonium salts;        the grafting of polymers from unsaturated organomagnesium compounds of RMgX type.        
The devices used to conduct such reactions generally comprise a tank to contact the substrate with the electrolyte, a counter-electrode and a light source.
Said devices have disadvantages however:                they do not permit uniform illumination of the surface of the substrate, the reaction is therefore not conducted uniformly;        no known device allows the conducting of electrochemical reactions activated by illumination on a substrate surface of greater size than a disc 50 mm in diameter;        no device permits uniform illumination of the semiconductor substrate without substantially perturbing the electric field lines in the electrolyte between the substrate and the counter-electrode.        
As a general rule, the notion of uniformity for said electrochemical reactions on the surface of semiconductor substrates, such as used in the microelectronics industry, is not described in any prior art document.
The descriptions of prior art devices remain very brief and only allow reactions to be considered on the scale of substrates having a size of a few cm2.